Enameled insulator bushing



1947- w. w. HIGGINS' 7 2,428,456

ENAMELED INSULATOR BUSHING Filed Au 27, 1945 2 Sheets-Sheet 1 rm 1 e"Kw/M ATTORNEY.

'Oct. 7, 1947.

W. W. HIGGINS ENAMELED INSULATOR BUSHING Filed Aug. :27, 1943 2Sheets-Sheet 2 [nun/1 ATTORNEY Patented Oct. 7, 1947 ENAMELED INSULATORBUSHING Waldo W. Higgins, Whitefish Bay, Wis., assignor to A. 0. SmithCorporation, Milwaukee, Wis., a corporation of New York ApplicationAugust 27, 1943, Serial No. 500,212

8 Claims.

This invention relates to enameled insulator bushing.

One of the objects of the invention is to provide a bushing of th coneshaped multiple disc type in which the discs are separated by and joinedto one another by ceramic enamel in a manner similar to the flat discbushing of applicants copending application Serial No. 441,199, filedApril 30, 1942, and issued August 6, 1946, to Patent No. 2,405,425.

Another object is to prevent the setting up of injurious stress in theenamel upon contraction of the discs and of the insulator in coolingfrom the temperatures employed in joining the parts.

Another object is to provide a method of constructing and assemblingconical-shaped discs for such an insulator, without distortion.

Other objects and advantages of the invention will appear hereinafter inconnection with a description of an embodiment of the inventionillustrated in the accompanying drawings.

In the drawings:

Figure 1 is a side elevation of the insulator, partially in section;

Fig. 2 is a similar View of the parts prior to joinder and in spacedrelation during assembly;

Fig. 3 is a similar view showing the parts assembled and weightedpreparatory to firing;

Fig. 4 is an enlarged fragmentary sectional view similar to Fig. 3; and

Fig. 5 is a view similar to Fig. 4 after firing.

The insulator comprises a conductor bushing I with a shank 2 and anintegral conical skirt 3 into which a plurality of conical insulatingdiscs or plates 4 fit. A core plate 5, of conical shape fitsinto thelast disc 4 and has a tubular shank 6 with a base 1.

The skirt 3, discs 4 and core plate 5 are coated with a high dielectricceramic enamel 8 fused thereto, as generally set forth in applicantscopending application. The enamel coating 8 extends over the meetingsurfaces of the parts and the inner edge surfaces thereof to provide acontinuous insulation therebetween. The coating 8 is crowned at thecentral circumference of th respective meeting surfaces as set forth insaid prior application and in applicants copending application SerialNo. 441,201, filed April 30, 1942, for Joinder of porcelain enameledproducts and issued July 2, 1946, to Patent No. 2,403,079.

The skirt 3, discs 4 and core plate 5 have outward flanges 9 extendingin planes perpendicular to the axis of the bushing and which may bethinner than the respective conical body mem- 2 bers to effectsubstantial spacing of the same so that they need not be completelycovered with dielectric enamel. It is preferable, however, to coat thesewith a thin coating of enamel to prevent scaling of the metal andpossible injury to the seal thereby.

The parts are assembled for joinder as indicated in Figs. 2, 3 and 4with the crowns of the coating 8 on the conical surfaces of the partsunder pressure contact from the Weight of the several parts and from theadditional weight It! applied on the top of the assembled structure.

A ring H is lowered onto the upper surface of the flange 9 on skirt 3,and has downwardly depending vertical rods l2 which engage the edges ofthe several flanges 9 to keep all of the parts in vertical alignment.The number of rods I2 employed may vary from three to several times thatnumber depending upon the size of the bushing, and the rods areuniformly spaced circumferentially about the structure.

Spacer blocks or washers i3 are assembled on each rod l2 and disposedloosely between the several flanges 9 at the time the discs areassembled, there being one washer between each two adjacent flanges oneach rod. The washers 13 are constructed of accurate thickness to limitthe coming together of the parts by softening and squashing of theenamel crowns during heating, so that the parts are kept concentric andin alignment and the required thickness of enamel is maintained betweenthe parts.

After the parts have been assembled, as shown in Figs. 3 and 4, they areheated in a suitable furnace to a temperature sufficient to effect anenamel flow, but substantially lower that the original firingtemperature of the enamel. The heat softens the enamel coatings and theyflow together allowing th parts to come together under the weight [9 andthe weight of the parts and the ring ll, rods I2 and spacers l3.

This lowering of the parts relative to one another continues until theflanges 9 engage the several spacer blocks [3 beneath them, therebylimiting further movement of the flanges. At this time the severalflanges are supported 0n the flange of core plate 5 by means of theseveral spacers l3.

The structure is then cooled and. thereafter the weight [0, spacers l3and ring H are removed. In order to prevent any undue stress being setup in the enamel upon cooling, the spacer blocks l3 should beconstructed of a metal having a higher coefflcient of thermal expansionthan the metal of the parts and the enamel. This will result in acontraction of the spacers I3 during cooling in excess of thecontraction of the bushing, so that as soon as the enamel becomessufficiently strong upon cooling it can assume the load without beingtensioned by the spacer blocks, and the latter can be readily removedwithout injuring the structure.

The weight employed for eifecting interfusion of the enamel coatingsshould be selected with regard to the strength of the flanges 9 at thehigh temperatures employed, and should not be sufficient to deflect ordistort the flanges. The flanges 9 may be continuous around thecircumference, or they may be discontinuous in the form of projectinglugs.

The spacers 13 may be employed to advantage in the construction of flatdisc bushings of the type set forth in applicants copending applicationabove referred to.

The invention may have various embodiments within the scope of theaccompanying claims.

I claim:

1. An insulator bushing of the cone-shaped multiple plate typecomprising cone-shaped metal plates coated with ceramic enamel andhaving circumferential flanges disposed in planes at right angles to theaxis of the structure and separated to provide for receiving spacingmeans therebetween during assembly and interfusion of the enamelcoating.

2. In the fabrication of insulator bushings of the ceramic enameledmultiple disc type, the employment of spacers of a thicknesscorresponding to the final axial spacing of the disc edges between theedges of the discs to prevent distortion of the structure duringinterfusion of the enamel coatings under pressure and determine thefinal thickness of enamel between the discs.

3. In the fabrication of insulator bushings of the ceramic enameledmultiple disc type, the steps of assembling the discs with theircoatings in pressure contact, positioning spacers loosely between theouter edges of the discs and distributed about the circumferencethereof, heating the structure to soften the enamel and eifect th'einterfusion of the coatings until said spacers become engaged by therespective discs and limit further movement thereof, cooling thestructure, and removing the spacers.

4. In the fabrication of insulator bushings of the ceramic enameledcone-shaped multiple plate type, the steps of assembling the plates withtheir axis vertical, applying a predetermined pressure weight on top ofthe assembled structure, applying spacer blocks of predeterminedthickness corresponding to the final axial spacing of the outer edges ofthe plates between the corresponding outer edges of adjacent plates anddistributed about the circumference thereof, heating the structure tointerfuse the enamel coatings on the adjacent plates while limiting theflow of the enamel by said spacer blocks, and thereafter cooling thestructure and removing the blocks.

5 In the fabrication of insulator bushings of the ceramic enameledmultiple disc type, the employment of spacer blocks of predeterminedthickness corresponding to the final spacing of the discs between thediscs to limit the flow of the enamel during interfusion thereof, anddistributing said blocks uniformly about the circumference of thestructure.

6. In the fabrication of insulator bushings cf the ceramic enameledmultiple disc type, the steps of placing spacer blocks of predeterminedthickness adapted to determine the final spacing of the discs and of ametal having a greater coefficient of thermal'expansion than that of theassembled structure between the discs to limit the flow of the enamelduring interfusion thereof, heating the structure to soften andinterfuse the enamel coatings of the several discs, and thereafter cooling the structure and thereby loosening the spacer blocks by reason oftheir greater contraction than the structure, and removing the spacerblocks.

7. In the fabrication of insulator bushings of the ceramic enameledmultiple disc type, loosely positioning spacer blocks between theassembled enamel coated discs, heating the structure to eifect a flowand interfusion of adjacent coatings While limiting the flow by means ofsaid spacer blocks, cooling the structure, and contracting the thicknessof the spacer blocks during coohng at a faster rate than the contractionof the structure to loosen the blocks for removal and prevent stressbeing set up in the structure by reason of the contraction of the sameupon the blocks.

8. In apparatus for use in assembling ceramic enameled multiple discinsulator bushings, spacer blocks of predetermined thickness relative tothe spacing of the discs to determine the final thickness of the enamelbetween the discs upon the fusion of the enamel 'by heat and pressure,and constructed of a metal having a greater coefficient of thermalexpansion than that of the finished structure.

WALDO W. HIGGINS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,997,109 Fyfe M Apr. 9, 19352,262,831 Burleson Nov. 18, 194.1 2,317,799 Pereles d. Apr. 27, 1M31,562,533 eintraub I Nov.2-l,1925 1,887,181 Cone Nov, 8, 1932 1,259,384Fortescue Mar. 12, 1918 FOREIGN PATENTS Number Country Date 253,575France 1924 (3rd addition to No. 559,864)

